(a) Field of the Invention
This invention relates generally to keypads for electronic equipment and in particular to a keypad which is resistant to electrostatic discharge through the keypad to the circuit board.
(b) Background Art
Electrostatic discharge through the keypad of a printer or other electronic equipment to the circuit board can damage the circuitry, cause the equipment to lose memory stored therein or cause the equipment to cease performing interrupts required for operation of the equipment. In some cases, the equipment may cease to function altogether. Thus, damage caused to printers, computers, and peripheral equipment by electrostatic discharge has long been known and efforts have been made to control the amount of electrostatic discharge near this electronic equipment.
In printers with keypads, one previous proposed solution has been to use a conductive material around the keypad which attracts the electrostatic discharge whereby the discharge is then carried through the grounding path of the product. This has proven unsatisfactory in that there is no control of the electrostatic discharge energy as the charge tends to induce magnetic fields and may also jump to adjacent devices thereby causing varying degrees of damage.